This invention relates to a vortex shedding device for use in measuring the rate at which air flows into the air intake of an internal combustion engine. The subject matter of this patent application is related to that of similarly entitled commonly assigned and concurrently filed U.S. Application Ser. No. 572,606 filed Apr. 28, 1975 in the name of Gary L. Innes.
Of the prior art references known by the inventor, U.S. Pat. No. 3,722,275 to Rodely et al and U.S. Pat. No. 3,818,877 to Barrera et al are believed to be the most pertinent to the present invention; the disclosure of the Barrera et al patent 3,818,877 is incorporated herein by reference. Other patents of interest include U.S. Pat. No. 3,756,078 to Yamasaki et al; U.S. Pat. No. 3,863,500 to Yamasaki et al; and U.S. Pat. No. 3,854,334 to Herzl.
The vortex shedding device of the invention is primarily intended for use in the engine compartment of a motor vehicle for the purpose of measuring the amount of air entering the air intake of the internal combustion engine located therein. The vortex shedding device utilizes electronic circuit means to determine the frequency or rate at which vortices are generated in air flowing past an elongated vortex generating element. Preferably, this circuit means includes means for measuring the temperature and pressure of the air entering the engine intake through the vortex shedding device. Such measurements of temperature and pressure are necessary for conversion of air flow velocity or volumetric flow rate to a mass flow rate as described in the aforementioned U.S. Pat. No. 3,818,877 to Barrera et al. The engine compartment of a motor vehicle is a very hostile environment for circuit means of the kind described, due to the high and wide range of temperatures encountered, presence of electromagnetic interference and corrosive atmosphere, etc.